The Friedmann equations, also known as the Friedmann-Lemaître or FL equations, are a set of equations in physical cosmology that govern the expansion...

Friedmann–Lemaître–Robertson–Walker metric (FLRW; /ˈfriːdmən ləˈmɛtrə ... /) is a metric based on an exact solution of the Einstein field equations of...

set of equations he developed known as the Friedmann equations. Alexander Friedmann was born to the composer and ballet dancer Alexander Friedmann (who...

field equations (EFE; also known as Einstein's equations) relate the geometry of spacetime to the distribution of matter within it. The equations were...

the dynamic cosmology of Alexander Friedmann. Removing the cosmological constant term from the Friedmann equations on the grounds that it was both unsatisfactory...

A de Sitter universe is a cosmological solution to the Einstein field equations of general relativity, named after Willem de Sitter. It models the universe...

In astrophysics, the Tolman–Oppenheimer–Volkoff (TOV) equation constrains the structure of a spherically symmetric body of isotropic material which is...

based his theory on the work of Einstein and De Sitter, and independently derived Friedmann's equations for an expanding universe. Also, the red shifts...

Functional equation Functional equation (L-function) Constitutive equation Laws of science Defining equation (physical chemistry) List of equations in classical...

Conference, the latter pointed out that Alexander Friedmann had proposed a similar solution to Einstein's equations in 1922, implying that the radius of the universe...

general relativity equations in 1922 by Alexander Friedmann. Friedmann published a set of equations, now known as the Friedmann equations, showing that the...

{\displaystyle C\ll c} for a "cold" gas. The equation of state may be used in Friedmann–Lemaître–Robertson–Walker (FLRW) equations to describe the evolution of an...

Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form...

the Robertson Walker scale factor, this is a key parameter of the Friedmann equations. In the early stages of the Big Bang, most of the energy was in the...

in the Friedmann equations, resulting in a model of the expanding universe known as the Friedmann–Einstein universe. In 1932, Einstein and De Sitter proposed...

Harry Friedmann (Hebrew: הארי פרידמן; 28 November 1931 – 28 May 2018) was a professor of chemistry who specialized in theoretical nonlinear optics and...

original general relativity equations that had been found by the mathematician Friedmann, working on the Einstein equations of general relativity. Einstein...

momentum equation, one arrives to: D u D t = T ∇ s − ∇ h {\displaystyle {\frac {D\mathbf {u} }{Dt}}=T\nabla \,s-\nabla \,h} Friedmann deduced this equation for...

by the cosmological principle and assumed by all models that use the Friedmann–Lemaître–Robertson–Walker metric, including the current version of the...

most accepted model explaining the evolution of our universe. The Friedmann equation defines how the energy in the universe drives its expansion. H 2 =...

variants of the original positive energy theorem. List of spacetimes Friedmann–Lemaître–Robertson–Walker metric Petrov classification, for algebraic...

vacuum, black hole mechanics, gauge-invariant linear perturbations of Friedmann-Lemaître cosmologies), Barry Barish (LIGO builder, gravitational-waves...

Raychaudhuri equation, or Landau–Raychaudhuri equation, is a fundamental result describing the motion of nearby bits of matter. The equation is important...

Willem de Sitter (6 May 1872 – 20 November 1934) was a Dutch mathematician, physicist, and astronomer. Born in Sneek, de Sitter studied mathematics at...

defining feature is its use of the Einstein field equations. The solutions of the field equations are metric tensors which define the topology of the...

relativity, the Hamilton–Jacobi–Einstein equation (HJEE) or Einstein–Hamilton–Jacobi equation (EHJE) is an equation in the Hamiltonian formulation of geometrodynamics...

In physics, the principle of relativity is the requirement that the equations describing the laws of physics have the same form in all admissible frames...

curvature is negative.[citation needed] From these assumptions and the Friedmann equations it follows that the scale factor must depend on time coordinate linearly...

theory dates back to 1922, with Russian physicist Alexander Friedmann creating a set of equations showing that the end of the universe depends on its density...

{\displaystyle \sum _{j=1}^{D-1}p_{j}^{2}={\frac {1}{D-1}}\neq 1.} The Friedmann–Lemaître–Robertson–Walker metric employed in cosmology, by contrast, is...